The term of “plant type” refers to a set of characteristics or an arrangement in space, i.e., features of growth and appearance, of a plant associated with the productivity of a crop variety. An ideal plant type, also called an ideotype, refers to an ideal type of plant formed of characters beneficial to plant photosynthesis, growth and development, and grain production, which allows for a maximal improvement of population optical energy availability, an increased biological yield, and an improved economic coefficient, etc.
One of the important factors of a plant type is plant height, which is not only a dominative factor affecting the plant type of a crop, but also an important agronomical character controlling the production. In order to improve the production of a crop, to facilitate a transition thereof from natural growth to targeted growth, and to lead the growth and development as well as appearance of a plant to promote high production, high quality, low consumption, and high efficiency, recently numerous experimental researches have been made on a production increasing effect of crop dwarfing. The results show that suitable dwarfing of a plant to increase population structure enables an increased production.
Cotton is one of the most important economic crops in China. Cotton is originally a ligneous perennial, and becomes an annual after a long-term naturalization, but retaining the character of indeterminate growth of a ligneous plant. However, big body with luxuriant foliage and spreading branches of the cotton plant often leads to shadowing in field, poor ventilation and light penetration, massive buds and bolls drop, and tendency to lodging, susceptibility of cotton bolls to pathogenic bacteria, formation of rotted and dead bolls, having a severe impact on the production and quality of cotton. Hybrid cotton predominates the south of China, where light, heat, and water are all sufficient during the growth of cotton, to make vegetative growth more vigorous. However, the plant type is more difficult to control, so that a high, big and hallow population tends to occur, resulting in a decreased production. Thus, development of an ideal plant type, and cooperation of the relations between plant development and external environment, vegetative growth and reproductive growth, and individual and population to provide a cotton plant with a reasonable development process adaptive to the characteristics of various ecological regions, is essential to achieve high quality and production of cotton. In the production of cotton, cultivation techniques are mainly used to lower plant height, shorten branches, and reduce leaf size. By way of controlling the growth of vegetative mass, facilitating growth of reproductive organs, to keep ventilation and light penetration in cotton field, to obtain more bolls per acre, and to regulate the economic coefficient of cotton, a higher production is achieved. Currently, among the main crops in China, rice and wheat are produced by use of dwarf varieties, but cotton is forcibly dwarfed by cultivation means, such as regulation with fertilizers, reduction of nutrient supply, inhibition of apical dominance by top pruning, chemical regulation with dimethyl piperidinium chloride (DPC), etc., which require consumption of a large number of labor and fossil energy, increasing costs for cotton production.